CLIMATOLOGY OF THE LOW LEVEL JET

Abstract

Geographical and diurnal variations in the frequency of occurrence of strong low level wind maxima are determined using 2 yr. of wind data from 47 rawinsonde stations in the United States. Maximum frequency of occurrence is found in the Great Plains at approximately 37°N. and 98°W. The vast majority of jets in this region occur with southerly flow. Southerly wind maxima appear on both morning and afternoon soundings but occur with much greater frequency, over a larger area, on the morning observations. Twenty-eight morning jet cases are used to determine average synoptic-scale wind and temperature patterns in the vicinity of the jet. Diurnal wind oscillations are examined by comparisons of jet frequencies, speeds, and altitudes on four-times-daily observations. The oscillation is similar to that described by Blackadar; however, there is no apparent tendency for the latitudinal variation in period of the oscillation which Blackadar's model implies.